# Math Help - Geometry experts, only (please).

1. ## Geometry experts, only (please).

Greetings. I need a geometry expert, please.

I have an 8 inch, 390 degree, chimney pipe coming into my basement at a 45 degree angle. I need to cut out a tin heat shield that lays flat against the wall, around the pipe. Obviously, it would be "eliptical-ish" (my word), but I wonder what the equation for this would be?

Thanks very much
Dave Vanwerkhoven

2. ## Re: Geometry experts, only (please).

I don't understand question
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3. ## Re: Geometry experts, only (please).

Originally Posted by Vanwerkhoven
Greetings. I need a geometry expert, please.

I have an 8 inch, 390 degree, chimney pipe coming into my basement at a 45 degree angle. I need to cut out a tin heat shield that lays flat against the wall, around the pipe. Obviously, it would be "eliptical-ish" (my word), but I wonder what the equation for this would be?

Thanks very much
Dave Vanwerkhoven
1. Draw a sketch (see attachment)

2. I assume that the 8' are refferring to the diameter? The minor axis has then the length b = 4. The major axis has consequently the length

$a = \frac{4}{\cos(45^\circ)}=4 \cdot \sqrt{2}$

3. The equation of the ellipse is:

$\frac{x^2}{32} + \frac{y^2}{16} = 1$